An ordinary starter for a small engine includes a driving pulley, a cam plate, a torque-accumulation spring and a casket. The driving pulley is fixed to a crank shaft of the engine. In the driving pulley, a centrifugal ratchet is provided to be engaged with a cam pawl provided in the cam plate. And, the casket is connected to the cam plate through the torque-accumulation spring.
To start the engine, the casket is rotated by a hand or a motor to accumulate a torque (energy) in the torque-accumulation spring. When the accumulated torque exceeds a rotational resistance of the engine, the accumulated torque is released at a stroke to the crank shaft through the cam plate and the pulley, thereby starting the engine (for instance, see JP-2002-227753-A).
That is, when such a torque as to exceed the rotational resistance of the engine is accumulated in the torque-accumulation spring, the engine can be rotated by the accumulated torque. However, the rotational resistance of the engine does not always have a constant resistance value. For instance, when a piston is located around an upper dead point, the rotational resistance of the engine becomes highest, and when the piston is located around a lower dead point, the rotational resistance of the engine becomes lowest.
When the rotational resistance is low, the torque accumulated in the torque-accumulation spring will be released even before the accumulated torque reaches a start torque necessary for starting the engine, and the cam plate will be rotated with an insufficient torque. In this case, since the torque transmitted to the driving pulley does not reach the start torque, the engine can not be assuredly started.
To solve this problem, a rotation regulation unit may be provided to regulate a rotation of a member such as a cam plate until a sufficient torque (energy) is accumulated in a torque-accumulation spring. The rotation regulation unit releases the accumulated torque after the sufficient energy is accumulated to thereby start an engine irrespective of a variation in the rotational resistance of the engine, and (see JP-2006-342717-A).
However, in JP-2006-342717-A, such rotation regulation unit is provided in a starter side. In this case, timing for starting an engine does not occasionally correspond to timing for releasing an accumulated torque due to the difference in types of engine or the variation in starter.
Further, when the starter is attached to the engine, the rotation regulation unit of the starter side needs to be aligned with a crank shaft of the engine side. Such operation is troublesome.